匀相沉淀法制备纳米Al2O3粉末

介绍了一种以工业用NH4Al(SO4)2*12H2O和NH4HCO3为原料采用匀相沉淀法制备纳米Al2O3粉末的新工艺,并研究了沉淀剂NH4HCO3的滴加速度、醇洗、表面活性剂等因素对Al2O3粒径的影响.研究结果表明,该工艺制备的粉体粒度均匀、平均粒径小于25nm.     

匀相沉淀法制备纳米Al_2O_3粉末

介绍了一种以工业用 NH4 Al(SO4 ) 2 · 1 2 H2 O和 NH4 HCO3为原料采用匀相沉淀法制备纳米 Al2 O3粉末的新工艺 ,并研究了沉淀剂 NH4 HCO3的滴加速度、醇洗、表面活性剂等因素对Al2 O3粒径的影响。研究结果表明 ,该工艺制备的粉体粒度均匀、平均粒径小于 2 5nm。     

共沉淀法制备Ca0.6Mg0.4Zr4(PO4)6纳米粉体

采用共沉淀法,以Ca(NO3)2·4H2O、Mg(NO3)2·6H2O、ZrO(NO3)2·8H2O和NH4H2PO4为原料合成Ca0.6Mg0.4Zr4(PO4)6(C0.6M0.4ZP)纳米粉体,通过TG-DSC、XRD、TEM和纳米粒度/Zeta电位分析手段研究了反应过程pH值、反应物浓度配比和沉淀反应方式等对合成粉体的相组成、平均颗粒尺寸及其分布等的影响.结果表明:将Ca2 、Mg2 、Zr4 离子混合溶液加入到不同pH值的NH4H2PO4溶液中,并控制pH=3～11,沉淀物经900℃煅烧3 h后,可合成单相的C0.6M0.4ZP纳米粉体;当Zr4 浓度为0.5 mol/L、沉淀剂NH4H2PO4浓度为1.0 mol/L、pH=9时,合成粉体平均颗粒尺寸和粒径分布范围最小,分别为40 nm和20～70 nm.     

热喷涂用镍包裹超细碳化钨复合粉体的制备

以Ni(NO3)2·6H2O和NH4HCO3为原料,采用非均相沉淀法在亚微米WC粒子上包裹一层镍的先驱体,再经高温分解和还原,在不同条件下制备了镍包裹WC复合粉体,并用SEM、TEM和XRD等对包裹粉的形貌和组成进行了分析。研究了沉淀剂的加入方式以及反应液浓度对包裹粉的影响。结果表明:当NH4HCO3以慢速加入,反应液浓度为0．14 mol／L时,可制备出粒径为1-2μm的包裹粉,且粒径分布均匀,分散性好,适合喷涂要求。     

沉淀包裹法制备Cu/α-Al2O3纳米复合粉体

以纳米Al2O3、CuSO4·5H2O和纳米铝粉为原料,采用非匀相沉淀工艺获得了纳米铜包裹α-Al2O3复合粉体;研究了反应温度和pH值对复合粉体成分及性能的影响;利用XRD、XPS、TG/DSC、Zeta电位和TEM等方法对复合粉体的成分、热学特性以及形貌特征进行了表征.结果表明采用反应温度为40℃、保温4 h的工艺条件,可以获得纳米铜颗粒包裹Al2O3纳米复合粉体,铜颗粒呈球形,尺寸为10 nm左右.     

化学沉淀法制备纳米Al_2O_3粉体中的反团聚研究

以工业用 NH4Al( SO4) 2 · 1 2 H2 O和 NH4HCO3为原料 ,采用化学沉淀法制备纳米Al2 O3粉体。研究了 p H值、乙醇、表面活性剂等因素对 Al2 O3粒子尺寸的影响 ,并探讨了几种反团聚的机理及效果。     

共沉淀法制备Ca0．6Mg0．4Zr4（P04）6纳米粉体

采用共沉淀法，以Ca（NO3）2·4H2O、Mg（NO3）2·6H2O、ZrO（NO3）2·8H2O和NH4H2PO4为原料合成Ca0．6Mg0．4Zr4（P04）6（C0．6M0．4ZP）纳米粉体，通过TGDSC、XRD、TEM和纳米粒度／Zeta电位分析手段研究了反应过程pH值、反应物浓度配比和沉淀反应方式等对合成粉体的相组成、平均颗粒尺寸及其分布等的影响。结果表明：将Ca^2＋、Mg^2＋、Zr4＋离子混合溶液加入到不同pH值的NH4H2PO4溶液中，并控制pH=3～11，沉淀物经900℃煅烧3h后，可合成单相的C0．6M0．4ZP纳米粉体；当Zr4十浓度为0．5mol／L、沉淀剂NH4H2PO4浓度为1．0mol／L、pH=9时，合成粉体平均颗粒尺寸和粒径分布范围最小，分别为40nm和20-70nm。     

共沉淀法制备纳米铈掺杂钇铝石榴石荧光粉及其荧光特性

以NH4HCO3、NH3·H2O混合溶液为沉淀剂,用共沉淀法结合后续煅烧制备了铈掺杂钇铝石榴石(YAG∶Ce)荧光粉,并采用热分析、红外光谱、X射线衍射、场发射扫描电镜等对粉体进行了研究,分析了铈掺杂浓度对粉体发射光谱和激发光谱的影响.结果表明:共沉淀法制备的铈掺杂钇铝石榴石经过1 000℃煅烧2 h,得到纳米晶YAG∶Ce荧光粉;随着铈浓度的增加,荧光粉发射光谱发生红移,激发光谱基本不变.     

化学法二步还原制备超细铜粉

以CuSO4溶液为原料,用葡萄糖作为预还原剂进行初步还原,用抗坏血酸进行二次还原,在不同的工艺参数下制备了超细铜粉;用激光粒度仪、SEM、XRD等对铜粉进行了表征.结果表明:较优的制备工艺为预还原时间90 min,溶液中Cu2+浓度0.2 mol·L-1,还原反应温度为80℃,溶液的pH值为14,葡萄糖浓度为0.05 mol.L-1,抗坏血酸浓度为0.025 mol·L-1;制备的铜粉平均粒径为8μm左右,粒径分布窄;铜粉形貌为各向生长均匀结晶良好的立方体、柱状或类球晶体;低温干燥后生成物为纯铜粉,未见Cu2O和CuO的特征峰.     

纳米氧化锡粒子的制备与性能表征

以SnCl4·5H2 O为主要原料 ,选择NH3 ·H2 O ,NaOH ,CO(NH2 ) 2 等不同沉淀剂制备出了纳米SnO2 粒子。采用TG DTA ,XRD ,TEM等测试手段 ,对纳米SnO2 粒子的结构和形貌进行了研究。结果表明 ,在 6 0 0℃下热处理得到的粒子结晶性能良好。改变反应条件 ,制备出了粒径分布窄、分散性良好的纳米SnO2 粒子 ,其平均粒径为 15nm。同时对用CO(NH2 ) 2 作沉淀剂反应形成纳米SnO2 粒子的机理进行了初步探讨     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.